21549836 has 96 divisors (see below), whose sum is σ = 50663424. Its totient is φ = 7776000.

The previous prime is 21549833. The next prime is 21549839. The reversal of 21549836 is 63894512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21549833) and next prime (21549839).

It is a self number, because there is not a number n which added to its sum of digits gives 21549836.

It is not an unprimeable number, because it can be changed into a prime (21549833) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 353246 + ... + 353306.

It is an arithmetic number, because the mean of its divisors is an integer number (527744).

Almost surely, 2^21549836 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21549836, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25331712).

21549836 is an abundant number, since it is smaller than the sum of its proper divisors (29113588).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21549836 is a wasteful number, since it uses less digits than its factorization.

21549836 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151 (or 149 counting only the distinct ones).

The product of its digits is 51840, while the sum is 38.

The square root of 21549836 is about 4642.1800912933. The cubic root of 21549836 is about 278.2795696969.

The spelling of 21549836 in words is "twenty-one million, five hundred forty-nine thousand, eight hundred thirty-six".